The invention relates generally to implantable medical devices and in particular to implantable medical devices for treating urinary incontinence.
Various implantable devices, such as distensible medical devices, are known in which the distensible medical devices are implanted into the tissue of a human to treat urinary incontinence. These devices have typically relied upon restricting or constricting the urethra of the patient to maintain continence.
U.S. Pat. No. 4,733,393 to Haber et al. is an attempt at such a proposed device. U.S. Pat. No. 4,733,393 relates to a hypodermically implantable genitourinary prosthesis which provides an extensible, inflatable tissue expanding membrane to be located in proximal urethral tissue to add bulk to these tissues for overcoming urinary incontinence by localized increase in tissue volume.
U.S. Pat. No. 4,802,479 to Haber et al. is an attempt at an instrument for dispensing and delivering material to an inflatable membrane of a genitourinary prosthesis within the tissues of a patient for overcoming urinary incontinence. U.S. Pat. No. 4,832,680 to Haber et al. relates to an apparatus for hypodermically implanting a genitourinary prosthesis comprising an extensible containment membrane for retaining a fluid or particulate matter which is injected from an external source.
U.S. Pat. No. 5,304,123 to Atala et al. relates to a detachable membrane catheter incorporated into an endoscopic instrument for implantation into the suburethral region of a patient. Also, U.S. Pat. No. 5,411,475 to Atala et al. discusses a directly visualized method for deploying a detachable membrane at a target site in vivo.
Once inflated, these devices maintain pressure on the urethra of the patient in an attempt to assist with continence. However, these devices are prone to being under or over inflated at time of implant, leading to undesirable postoperative results. For example, if the devices are overinflated it may cause the urethra to be restricted too tightly, and the patient is at risk for retention, a condition where the patient cannot pass urine. Such a condition could lead to kidney damage, necessitating major corrective surgery or at minimum use of self-catheterization to empty the bladder on a regular basis thus increasing the risk of urinary tract infection.
Furthermore, once these devices have been implanted within the patient, the only means of removing them in the event of a postoperative problem or device malfunction is through major surgery. Also, the devices are secured within the tissues of the patient, so there is the possibility of the devices migrating back along the pathway created in inserting them, a problem which has been noted with prior art devices. Thus, an important medical need exists for an improved implantable device for treating urinary incontinence.
The present invention provides an implantable device and a method for its use in restricting a body lumen. In one embodiment, the body lumen is a urethra, where the implantable device is used to coapt the urethra to assist the patient in urinary continence. The implantable medical device has the advantage of being adjustable both at the time of implantation and postoperatively. This postoperative adjustability of the implantable medical device allows a physician to regulate the amount of pressure applied to the urethra to ensure continence of the patient and to minimize iatrogenic effects.
In one embodiment of the invention, a patient""s incontinence is treated by positioning one or more of the implantable devices adjacent to at least one side of a patient""s urethra so as to adjust liquid flow resistance in the urethra. This is accomplished by using the implantable devices to coapt the patient""s urethra so as to maintain a transverse cleft or slit structure of the collapsed urethra and thereby provide sufficient flow resistance to ensure continence, while still allowing the patient to consciously discharge urine when necessary.
The device according to one embodiment of the invention is intended to work immediately adjacent to the urethral wall of a patient to create an increase in urethral coaptation and flow resistance. However, in the prior art devices any tissue change which may occur postoperatively such as a reduction in tissue edema associated with the procedure may cause a reduction in clinical effect because of the reduced coaptation and resistance after the swelling has subsided. Although some minor degree of adjustability is available at the time of implantation in the prior art devices, not until the availability of the present invention is it possible to access the implanted device and adjust the membrane volume after implantation in a postoperative manner.
In one embodiment, the implantable device for treating urinary incontinence comprises an adjustable element having a continuous wall or membrane, where the wall includes an inner surface defining a chamber. The continuous wall is constructed of at least one material that is substantially self-sealing, and therefore, is able to withstand multiple punctures, for example from non-coring hypodermic needles, during postoperative adjustments of the adjustable element.
In one embodiment, the continuous wall is constructed of a biocompatible resiliently elastomeric polymer or polymer blend of polyurethane, silicone, or the like. In an additional embodiment, the continuous wall of the adjustable element has an outer surface generally defining a sphere. In yet another embodiment, the continuous wall has an outer surface generally defining an elongate body having semi-spherical end portions.
During the postoperative adjustments, the adjustable element is expanded or contracted (i.e., the volume of the adjustable element is increased or decreased) due to fluid volume introduced into the chamber. In one embodiment, fluid volume is introduced into the chamber through a hollow non-coring needle, such as a hypodermic needle, inserted through the wall of the adjustable element. The self-sealing ability of the wall allows for such adjustments by needles during one or more postoperative occasions without compromising the pressure retaining ability of the wall of the adjustable element.
In an additional embodiment, the implantable device includes one or more reinforcing structures positioned between the inner surface and an outer surface of the continuous wall. In one embodiment, woven or layered fibers of polyester, nylon, polypropylene, polytetrafluoroethylene (such as TEFLON) or other polymers having a high durometer measure or high modulus constitute the reinforcing structures. The reinforcing structures help to maintain structural integrity and the shape of the adjustable element during the initial inflation and any postoperative adjustments made thereafter.
In an additional embodiment, the continuous wall of the adjustable element has a porous polymer structure that allows the movement of water between the outer surface and the inner surface. A hydrophilic polymer is substantially encapsulated in the chamber, where the hydrophilic polymer absorbs water to expand the implantable device. Once implanted within a patient, the volume of the adjustable element is altered (i.e., expanded or contracted) during implantation and/or postoperatively by introducing or removing the hydrophilic polymer from the chamber. In one embodiment, the hydrophilic polymer is hyaluronic acid, polyvinylpyrrolidone, polyethylene glycol, or carboxy methyl cellulose.
In an additional embodiment, the implantable medical device includes a tubular elongate body connected to and sealed to the adjustable element. The tubular elongate body includes a first interior passageway extending longitudinally in the tubular elongate body from a first port at the proximal end to a second port in fluid communication with the chamber of the implantable device for adjustably expanding or contracting the expandable element by applied fluid volume introduced through the first port.
The tubular elongate body further includes a second interior passageway extending longitudinally in the tubular elongate body from a proximal opening through the peripheral surface positioned between the proximal and the distal end to a distal opening through the distal end of the tubular elongate body. This second interior passageway is of sufficient diameter to receive and guide an obturator for the insertion of the implantable device into a human body.
This embodiment of the implantable device also includes a rear port element coupled to the proximal end of the tubular elongate body. The rear port element including a cavity in fluid communication with the first port of the first interior passageway. An elastic septum is included on the rear port element, and is retained in the rear port element by a clap ring located around the rear port element.
An important improvement provided by one embodiment of the present invention resides in the ability to access the implanted rear port element located close to the surface of the patients skin to adjustably restrict the urethra. This is accomplished by controlling the volume of a fluid, such as a flowable material, in the adjustable element after it has been implanted in the patient. Suitable flowable materials for introduction into the expandable membrane include a saline liquid, a flowable gel, or a slurry of small particles such as silicone in a fluid carrier. Moreover, the flowable material may be made radiopaque to facilitate fluoroscopic visualization for postoperative inspection.
The post implantation, or postoperative, urethral restriction is realized by the adjustable element acting on tissue adjacent to the walls of the urethral lumen and forcefully closing the urethral lumen. Voiding of urine from the bladder only occurs when the intravesicular pressure overcomes the resistance established by the adjustable element.
An important feature of the implantable device of the present invention relates to the adjustable element or membrane which is accessible for subsequent adjustment in volume through the rear port element located under a patient""s skin, remotely from the adjustable element. Another important feature of the present invention over the prior art devices is the convenient in vivo postoperative adjustability of both pressure and size of the adjustable element.